Turbines which are utilized with hot fluids experience dimensional changes during the operation of the turbine as a result of substantial temperature changes in the components of the turbine. For example, during operation, portions of a steam turbine can reach temperatures which are sufficiently elevated that the elongated components, such as the turbine shaft and the turbine case, experience substantial increases in their length, which must be taken into account in designing the mechanical support for the turbine. One technique has been to provide a bearing case at one end of the turbine shaft, with the bearing case being mounted on flexible supports, while the other end of the turbine shaft is mounted on fixed supports. In one such system, each of the four corners of the bearing case is mounted on a flex plate support having one or more vertical plates which provide vertical support, but which flex relatively easily in a direction parallel to the longitudinal axis of the turbine shaft. However, the inboard end of the bearing case, i.e., adjacent to the turbine casing, experiences operating temperatures which are substantially higher than the operating temperatures of the outboard end of the bearing case, i.e., remote from the turbine casing. This difference in operating temperatures results in the two flex plate supports at the inboard end of the bearing case experiencing greater thermal expansion than the two flex plate supports at the outboard end of the bearing case, such that the elevation of the inboard end of the bearing case becomes higher than the elevation of the outboard end of the bearing case, resulting in a deviation in the orientation of the bearing case with respect to the longitudinal axis of the turbine shaft. This deviation in orientation can cause severe damage to the bearings as well as to other parts which become misaligned with the turbine shaft as a result of the deviation.
Accordingly, there is a need for providing for axial expansion of a turbine machine during operation while avoiding deviations in the orientation of the turbine shaft with respect to the support bearings for the turbine shaft, and to other components positioned by the bearing case.